• Journal of Climate Change Research
• /
• v.8 no.2
• /
• pp.163-169
• /
• 2017

In this study, Non-$CO_2$ emission factors were estimated for the coal briquette boiler, which is the Korean heating system. As a result, the $CH_4$ and $N_2O$ emission factors of the coal briquette boiler were estimated to be $11.76gCH_4/TJ$ and $7.44kgN_2O/TJ$, respectively. The results showed that $CH_4$ emission factor was 12 times and $N_2O$ emission factor was 5 times higher than IPCC default value. Also the emission factors developed in this study were compared with a precedent study. The results indicated that were similar to open the air inlet of coal briquette stove because the combustion condition of this study was similar to that of coal briquette stove.

• Journal of Energy Engineering
• /
• v.27 no.4
• /
• pp.13-19
• /
• 2018

In this study, the lightweight design of butterfly valve disc component for power plant based on topology optimization was performed. Here, commercial finite element (FE) analysis software was used. The external shape of the basic disc model was not deformed, and the internal element density was removed to make it lightweight. Optimal design was performed each other after the disc plate and two brackets attached on the surface of the disc were separated. Once the optimal shapes were selected, they were assembled to build up the 3-D lightweight valve disc model. After applying pressure to this model, FE analysis was performed to confirm the structural safety.

• Journal of the Korean Solar Energy Society
• /
• v.39 no.3
• /
• pp.19-27
• /
• 2019

In commercial areas, outdoor units are typically installed close to one another in the narrow space between buildings due to insufficient regulations. This makes it difficult to ventilate the discharge airflow, which may lead to deterioration of the performance of outdoor units. This study conducted CFD simulation to analyze the thermal environment according to the installation distance of the outdoor unit. The outdoor unit was installed in the space between buildings, and the thermal environment was analyzed by changing installation distance and wind speed. The performance of the outdoor unit was evaluated by measuring the on-coil temperature. The results show that the closer the distance between outdoor units, the higher the condenser on-coil temperature. Also, the on-coil temperature appeared to rise dramatically at lower wind speed.

• Journal of the Korean Solar Energy Society
• /
• v.39 no.1
• /
• pp.41-49
• /
• 2019

In this study, we analyzed the relationship between four elements: long-wave radiation, the direction of the building, BVR (Building View Ratio), and cloud amount. We examined how long-wave radiations surrounding a building influences the perception of heat in the summer. The results are as follows. (1) Long-wave radiation and BVR are highly correlated regardless of geographical direction. (2) Especially, during dawn in a clear day, areas with high BVR observed high levels of long-wave radiation. (3) This correlation suggests that higher BVR in urban areas will result in a greater number of tropical nights.

• Journal of the Korean Solar Energy Society
• /
• v.39 no.4
• /
• pp.11-24
• /
• 2019

The total solar irradiation on horizontal surfaces is separated into the beam and diffuses components. Although horizontal global irradiance is a commonly measured parameter for many sites, horizontal diffuse irradiance is not so readily obtainable. For such sites that measure global irradiation alone, a simple but reasonably accurate method is required to estimate diffuse irradiance from its global counterpart. This study investigates the applicability of correlation coefficients models correlating hourly diffuse and beam fraction and hourly clearness index in Daejeon. The three diffuse to global correlation coefficients models (Orgill and Holland model, CIBSE Guide J model, and Erbs et al. model) are selected and the three modified beam to global correlation coefficients models are generated. MBE, RMSE, r-squared of Daejeon and Daejeon boundary site-fitted models are compared with the case of original coefficients. The comparison result shows that the beam and diffuse to global solar irradiation correlation coefficients models with boundary site-fitted coefficients are best suitable for Daejeon. Further researches will be conducted to find the boundary site-fitting method using measured data of other cities and correlation coefficients models using solar altitude, cloud cover, and sunshine duration.

• Journal of Hydrogen and New Energy
• /
• v.32 no.6
• /
• pp.464-469
• /
• 2021

A reforming catalyst for hydrogen production from ammonia is being studied. Non-novel metal based Ni catalysts for use in ammonia reforming processes are being developed. In this study, the ammonia reforming characteristics according to Ni content of the alumina pellet supported catalyst in the mid-temperature region were investigated under different space velocity. 20 Ni and 3,000 h^-1 showed the best catalytic activity with ammonia conversion of 63% among all conditions.

• Tunnel and Underground Space
• /
• v.32 no.6
• /
• pp.386-396
• /
• 2022

To analyze the influence of variables of roadheaders, the linear cutting testing data of pick cutter were collected from the former literatures. The input factors were set up as uniaxial compressive strength, cutting depth, cutting spacing, attack angle, skew angle, and output factors were determined as specific energy, average cutting force, maximum cutting force, average vertical force, and maximum vertical force. After composing a table of the design of experiment (DOE). The contribution level of each factor was calculated by analysis of variance (ANOVA). As a result, the factors having greatest influence on cutting force and specific energy were uniaxial compressive strength and cutting spacing.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.247-247
• /
• 2022

제트류는 복잡한 흐름 중 하나로 다양한 크기의 에디가 다양한 운동량을 가지고 있다. 이러한 제트류를 구현하기 위해서는 난류 운동 에너지 등 제트류의 특성을 잘 반영하여야 한다. 제트를 구현하기 위해서는 수리학적 모델, 현장 실험 등 많은 방법이 있으며, 본 연구에서는 상대적으로 공간, 시간적 비용이 적게 드는 수치해석 방법을 사용하여 연구를 진행하였다. 대표적인 수치해석방법에는 DNS(Direct Numerical Simulation), LES(Large Eddy Simulation), RANS(Reynolds Averaged Navier Stokes) 등이 있다. RANS는 시간 평균 흐름 특성만 산출하며 제트의 복잡성을 재현하는 데 한계가 있어, 본 연구는 DNS와 LES 모델을 이용하여 제트류를 구현하는 것에 초점을 맞추었다. DNS는 해당 격자에서 발생하는 모든 에디를 직접 해석 때문에 난류 모델링이 필요하지 않지만, 많은 수의 그리드가 필요하여 수치해석 시 소요시간이 긴 편이다. LES는 대규모 에디는 직접 해석하지만 일정 크기 이하의 소용돌이를 해석하기 위해서 모델이 필요하다. 따라서 서브 그리드 모델에 따라 약간 다른 결과를 보인다. 이러한 문제점을 해결하기 위해 본 연구에서는 LES의 기존 서브 그리드 모델을 사용하지 않고 신경망 모델로 학습한 DNS 결과를 활용하는 방법을 제안한다. 우선 DNS와 LES 모델을 사용하여 에너지 스펙트럼을 비교하여 서브 그리드 모델이 시작하는 파수를 찾는다. 이후 특정 파수 아래의 작은 에디를 모사할 적절한 신경망 모델을 결정하여 DNS의 작은 에디를 신경망 알고리즘이 모사할 수 있도록 학습시킨다. 이후 기존 서브 그리드 모델을 사용하지 않고 학습된 신경망 알고리즘을 사용한 LES 모델이 모사한 제트류와 실제 DNS 모델을 사용한 제트류를 비교 및 평가한다.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2023.01a
• /
• pp.43-46
• /
• 2023

호흡기 관련 전염병의 주된 증상인 기침은 공기 중에 감염된 병원균을 퍼트리며 비감염자가 해당 병원균에 노출된 경우 높은 확률로 해당 전염병에 감염될 위험이 있다. 또한 사람들이 많이 모이는 공공장소 및 실내 공간에서의 기침 탐지 및 조치는 전염병의 대규모 유행을 예방할 수 있는 효율적인 방법이다. 따라서 본 논문에서는 탐지해야 하는 기침 소리 및 일상생활 속 발생할 수 있는 기침과 유사한 배경 소리 들을 Mel-Spectrogram으로 변환한 후 시각화된 특징을 CNN 모델에 학습시켜 기침 탐지를 진행하며, 일반적으로 사용되는 사전 학습된 CNN 모델에 제안된 Attention 모듈의 적용이 기침 탐지 성능 향상에 도움이 됨을 입증하였다.

• Journal of Wind Energy
• /
• v.14 no.3
• /
• pp.69-82
• /
• 2023

Offshore wind farms (OWFs) should be promoted as part of global efforts to respond to climate change, and efforts to preserve biodiversity in terms of climate change adaptation should also be considered. However, the ecological status of marine birds related to OWFs on the Korean Peninsula, such as habitat and reproduction, are not well known. In this study, ecological reasons for the reproductive status of Black-tailed gulls in Korea and representation related to OWFs, the evaluation direction of marine birds related to OWFs was presented. In a review of the techniques for monitoring marine birds, it was confirmed that Korea also needs to provide basic status information on marine birds at the national level. In addition, this study analyzed the reproductive status and related research status of Black-tailed gulls, an important indicator and dominant species on the Korean Peninsula, in relation to marine development projects including OWFs. Furthermore, the direction of environmental impact assessment preparation and impact prediction for various development projects promoted in the ocean, such as OWFs, was considered.